1. Field of the Invention
The present invention relates to a gas turbine intake air cooling apparatus and, more particularly, to a gas turbine intake air cooling apparatus utilized for increasing the output of the gas turbine facilities of a combined cycle power plant.
2. Description of the Related Art
In recent years, thermal power plant facilities are being shifted to combined cycle power plants having an improved thermal efficiency in order to renew old single cycle power plants.
Different from a single cycle power plant, a combined cycle power plant has a gas turbine in place of a conventional boiler, and generates electric power with a generator driven by this gas turbine and a generator driven by a steam turbine that receives steam from a waste heat boiler utilizing exhaust gas of the gas turbine. The efficiency of the combined cycle power plant is improved over that of the single cycle power plant by about 10%.
The gas turbine used in the combined cycle power plant generates a high-temperature high-pressure gas by causing combustion of compressed air with fuel, and rotates the turbine with this gas, thereby obtaining power.
An output from the gas turbine is influenced by the temperature and humidity of the combustion air. More specifically, the output from the gas turbine is related to the amount of oxygen (amount of air) that can be taken. The larger the amount of intake air and the lower the air temperature, the higher the output from the gas turbine.
The larger the moisture content in air, the larger the amount of water vapor in the high-temperature high-pressure gas. Latent heat of the water vapor, after being cooled by the waste heat boiler, is not used but is discharged to the outside. Thus, the smaller the moisture content (humidity) in intake air, the higher the output of the combined cycle power generation.
Accordingly, the output performance of the combined cycle power plant differs between summer and winter. In particular, as the power demand reaches the peak in the daytime of summer, a decrease in output of the combined cycle power generation poses a serious problem.
A freon-free absorption type refrigerating machine or HP (Heat Pump) attracts attention as freon destroys the ozone layer. As this absorption type refrigerating machine does not use electricity as the drive source but can utilize steam and exhaust gas, it is promising as a device for leveling the power load of summer.
A currently proposed gas turbine air cooling apparatus utilizes latent heat of ice. This apparatus stores cold heat by an electric refrigerating machine in the form of ice at night when the power demand is low, extracts this cold heat during the daytime power peak hours, and cools the intake air of the gas turbine with the cold heat.
More specifically, the refrigerating machine is operated at night by using seawater or the like as the cooling water. Ice is stored in an ice storage tank. This ice is thawed during the daytime peak hours, and supplied in the form of cold water to an air-cooling heat transfer (air cooler) installed to the intake channel, thereby cooling the intake air of the gas turbine.
However, in the ice storage tank of the gas turbine intake air cooling apparatus described above, the ice must be thawed at a high speed. Also, since the intake temperature must be decreased, the temperature of the water returning from the air cooler cannot be increased too much. Then, the following problems arise.
In the conventional gas turbine intake air cooling apparatus, as ice making is performed between night and the daytime peak hours and the obtained cold heat is extracted within 2 to 4 hours during the daytime peak hours, the amount of cold water circulating between the ice storage tank and the air cooler is very large, which is about 4 to 6 times that of a conventional air-conditioning large-size ice storage system.
When the flow rate of circulating cold water is increased, the residence time of the return water in the ice storage tank becomes short. As the cold water is circulated before the ice in it is sufficiently thawed, the intake temperature of the cold water is increased. Even if the ice storage tank stores ice, the intake air cannot be cooled to a predetermined temperature.
The gas turbine intake air cooling apparatus described above has a problem in the amount of ice in the ice storage tank. When the amount of ice is small, the size of the ice storage tank itself is increased.
Moreover, other major large-size constituent equipments are a refrigerating machine and a air-cooler. Therefore, it is difficult to put a gas turbine intake air cooling apparatus into a practical use in terms of cost and space.